Remove Emscripten support

lib/Target/JSBackend/JSTargetMachine.cpp

-//===-- JSTargetMachine.cpp - Define TargetMachine for the JS -------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the JS specific subclass of TargetMachine.
-//
-//===----------------------------------------------------------------------===//
-
-#include "JSTargetMachine.h"
-#include "JSTargetTransformInfo.h"
-#include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/Support/TargetRegistry.h"
-using namespace llvm;
-
-JSTargetMachine::JSTargetMachine(const Target &T, StringRef Triple,
-                                 StringRef CPU, StringRef FS, const TargetOptions &Options,
-                                 Reloc::Model RM, CodeModel::Model CM,
-                                 CodeGenOpt::Level OL)
-    : TargetMachine(T, "e-p:32:32-i64:64-v128:32:128-n32-S128", Triple, CPU,
-                    FS, Options) {
-  CodeGenInfo = T.createMCCodeGenInfo(Triple, RM, CM, OL);
-}
-
-
-TargetIRAnalysis JSTargetMachine::getTargetIRAnalysis() {
-  return TargetIRAnalysis(
-      [this](Function &F) { return TargetTransformInfo(JSTTI(this, F)); });
-}